1. Field of the Invention
This invention relates to certain polybutadiene-based resins, curable by peroxy initiation, and having improved thermal, impact, and cure-through-volume properties. More specifically, it relates to resins which may be viewed as a reaction product of, e.g., polybutadiene diols and their acrylonitrile copolymers with, e.g., methacrylate-capped aromatic diisocyanates.
2. Prior Art
It is known that curable resins having desirable properties may be prepared as the reaction product of an organic polyisocyanate and an acrylate ester having an active hydrogen in the non-acrylate portion of the ester. Such resins are disclosed in U.S. Pat. No. 3,425,988 to Gorman et al. This patent relates specifically to monofunctional, acrylate-terminated material which is reacted with organic polyisocyanate in such proportions as to convert all of the isocyanate groups to urethane or ureide groups. The acrylate esters are preferably the acrylates and methacrylates containing hydroxy or amino functional groups on the non-acrylate portions thereof.
U.S. Pat. No. 3,678,014 to Suzuki et al. discloses a peroxide-curable thermosetting resin comprising a reaction product of a polybutadiene or copolybutadiene having a preponderance of the 1,2-configuration of butadiene units and terminated with hydroxyl or carboxyl groups, and an isocyanate compound obtained by the reaction of an organic polyisocyanate with an olephinic compound such as a hydroxyalkyl acrylate or hydroxyalkyl methacrylate. The resins so produced are curable with peroxy initiators and are said to be useful as coatings or adhesives. Such resins are not fully satisfactory in terms of various properties, such as impact strength, thermal strength (i.e., strength at high temperatures or after high-temperature aging), and, moreover, do not have the ability to cure satisfactorily through relatively large gaps, e.g., approximately 40-50 mils or more.
U.S. Pat. No. 3,674,743 to Verdol et al. tracks self-curing solid elastomers made by reacting a polyfunctional, hydroxyl-reactive compound (e.g., a polyisocyanate) with a polyhydroxyl polymer. That polymer is made from a 1,3-diene having about 40-70 percent trans-1,4-unsaturation and about 10-30 percent cis-1,4-unsaturation. The elastomeric product is useful as a binder, coating, etc., and is stated to have certain improved properties, e.g., flexibility and tear strength. However, the product is not known as an adhesive, no thermal or cure-through-gap properties are suggested, and no particular advantage is attributed to the 1,4-unsaturation. Moreover, the product is not acrylate/methacrylate-terminated and thus is fundamentally different in structure from the compounds of the present invention.
U.S. Pat. No. 3,431,235 to Lubewitz discloses the cyclization of a reaction product of, e.g., hydroxyl-terminated 1,2-polybutadiene with toluene diisocyanate. While this results in certain useful properties, the heat stability, cure speed, and cure-through-volume properties are unsatisfactory.